In recent years, demand for quieter vehicles has been increasing, and demand for noise reduction in vehicle parts has become very immediate. Particularly in auxiliary machines that rotate at comparatively high speeds, especially automotive alternators, there is an urgent need for reductions in magnetic noise that is generated as a result of power generation and that constitutes one cause of noise generation.
Known examples of automotive alternators that are aimed at preventing such generation of magnetic noise include the automotive alternator that is described in Japanese Patent Laid-Open No. HEI 8-7-554 (Gazette), for example.
That generator includes: a shaft; a rotor that is fixed to the shaft; a stator that has a stator core that is disposed so as to surround an outer circumference of the rotor and in which a plurality of slots that extend axially are formed so as to be spaced apart circumferentially; and a front bracket and a rear bracket that hold circumferential edge portions of the stator core from two axial ends using a plurality of holding means and that envelope the stator core, wherein a pair of stays that are formed on the front bracket are fixed to a vehicle by a fastening means that penetrates through a pair of penetrating apertures that are respectively formed on the stays.
In the case of that generator, propagation of vibrations from the engine through the stays to the bracket is reduced by disposing reinforcing ribs on the stays that are formed on the front bracket and the rear bracket to reinforce the strength of the bracket, and amplification of magnetostriction is suppressed and generation of unpleasant magnetic noise is prevented by preventing deformation of the bracket and the stator core that deform as a result of such vibrations.